Well. I think Fredo explained it very well…
What you ask is what’s implemented in protools. Nuendo is different.
None of the two systems as they are today is perfect, but with time, nuendo seems way more logic to me.
Especially if they finally implement what Fredo suggested.
And for the record, what you ask is already there (all channels same param) with good implemented vst3 plugins (ie not waves, which are clearly PT aimed and badly vst3 implemented).
What’s missing in nuendo is just the ability to make different adjustments on different channels/group of channels inside the same plugin instance…
I’m afraid that in your case, the workaround is the only solution… Or you have to reconsider your routing to take this phenomenon into consideration, which could be more annoying than the workaround ;-(